Gradual initiation of trimethoprim/sulfamethoxazole as primary pneumocystic carinii pneumonia prophylaxis. Results of an ad hoc interim review committee: study doing well in terms of recruitment and data accuracy. As of 12-14-95, 301 subjects of a planned accrual goal of 380 were enrolled. Committee also noted a higher than expected number of study endpoints. Discontinuation due to adverse events attributed to the drug.